Difference between a 3.0 that's been modded to 3.2 and a real 3.2?

[Hotwatermusic]

I have a 3.0 SC engine that the PO had modded to a 3.2. Aside from still having CIS, how different is this motor from the real 3.2's that came later, power-wise and reliability-wise? Is changing the 3.0 to a 3.2 "bad" for it any way; is it pushing it harder than it was designed for, etc.? Are there things I need to be careful off or watch out for more than a stock 3.0 SC engine?

[James Brown]

can't be done, totaly different engine. NOT a CIS injection on the 3.2 unless they went through the HELL of just changing the pistons and cylinders (don't think you can do that easly) or put a CIS on a 3.2...... I would check with the "po" and if it is a 3.0 w/bigger p/c, you not gaining much HP.

[Geronimo '74]

Originally Posted by James Brown

can't be done, totaly different engine. NOT a CIS injection on the 3.2 unless they went through the HELL of just changing the pistons and cylinders (don't think you can do that easly) or put a CIS on a 3.2...... I would check with the "po" and if it is a 3.0 w/bigger p/c, you not gaining much HP.

I think thats what the OP said. PO changed 3.0 into a 3.2 by changing P/C.
Only the displacement went from 3.0 to 3.2. I believe the rest has not been changed. Am I correct?
Displacement increase would not mean a massive HP gain, in this case, I reckon.

[psalt]

Hotwatermusic,

To answer your question on durability, just the opposite is true. If done correctly (a big if), a short stroke 3.2 is under less stress and is mechanically stronger than a stock 3.2. In terms of output, it depends on what else was done to the engine. If just the displacement increase and no change in compression, the factory 3.2 may have a slight hp advantage, but torque would be very similar. Nothing to worry about.

[longhornchris04]

Well, an engine is clearly more than just its displacement, but here are a few insights.

1: an SC motor conversion to a 3.2 is (most often) done by replacing the 95mm pistons & cylinders with 98mm P&Cs. This combination is commonly referred to as a 3.2 Short Stroke (3.2SS). The Carrera 3.2 uses 95mm P&Cs with a different crank & connecting rods. Thus, it has a longer stroke with the same bore as an SC.

2: Larger displacement produces more power, but large bore -short stroke engines tend to be able to run higher rpms vs. small bore - long stroke engines which tend to produce more torque. This has to do with the ability of the engine to handle internal stresses... and assumes same/similar materials and appropriate camshafts. Short stokes are under less stress at high RPMs than longer stroke engines.

3: Camshaft & induction are still going to be the driving factor. A 3.2SS and a 3.2 with the same camshaft and Carbs (for example) should be nearly identical. The difference in engine geometry would become apparent if the camshafts were custom chosen.

4: The 3.2 had better head geometry than the SCs. Now, its possible to port the 3.0 heads to the 3.2 specs (or better). Additionally, while this makes a difference, its marginal and easily overwhelmed by other factors.

As to your original question - without knowing the internals its tough to compare your 3.2SS to a stock 3.2, but I can say the following:

1: If you've got CIS still, the stock 3.2 will be better performing -- Bosch DME is better than CIS, especially for performance.
2: CIS requires "mild" camshafts -- Thus your limiting factor on performance will be running out of breath (camshaft) or valve float - not connecting rod strength.

I have to go to work, but if I think of anything else, I'll come back.

[Paulporsche]

PM Gunter. I'm sure he'll have a lot to say about this.

Bruce Anderson has a section on this mod in his Performance Handbook. I think he said that back in about 1980 it was common for German tuners to do the 3.2 mod c/w a freeflow exhaust, no cat and about a 10:1 CR and net about 220 hp.

[La Quinta]

I have a 1977 Carrera 3.0 with a proper 98mm conversion using Mahle Pistons and barrells. The engine was balanced to within 1gm during the rebuild and the ports and manifolds were matched. With SSI exhaust and new matched injectors the car delivers 205 bhp at the rear wheels. A big improvement on a claimed 200bhp at the flywheel.
Pressure fed tensioners and Dilivar studs were also included. The familiar Carrera 3 surge from 4000 rpm starts at about 3400rpm and it pulls so strongly at the top end the rev limiter is easily activated in 5th gear.
The car is on 7 and 8 x 16 with Bridgestones SO2 Uprated Bilsteins and thicker torsion bars and rear ARB

[Gunter]

Originally Posted by Hotwatermusic

I have a 3.0 SC engine that the PO had modded to a 3.2. Aside from still having CIS, how different is this motor from the real 3.2's that came later, power-wise and reliability-wise? Is changing the 3.0 to a 3.2 "bad" for it any way; is it pushing it harder than it was designed for, etc.? Are there things I need to be careful off or watch out for more than a stock 3.0 SC engine?

Good stuff but we need to know more.

Find out from the PO what the compression ratio is for the P/C's.
And, what cams were used? 964 ?
Is this a '78-'79 engine or a '80-'83?
With SSI heater boxes and what muffler?

Common practice is/was to bolt on the larger P/C's but also to regrind the cams to a different profile like 964 with CIS. Installing SSI heaterboxes and a muffler with free-flow gives a few more horses. If your engine is a '80-'83, I'd recommend the use of the CIS and ignition distributor from a '78-'79 plus bore out the ports on the heads to match the larger intakes. If your engine is a '78-'79, no need to do that.

It is true that the short-stroke crank 70.4 mm likes to rev.
A noticeable kick comes in after 4000 RPM.
I kept CIS, 9.8 CR, 964-cams, SSI's..............and figure it adds about 30-35 HP.

Let us know more details.

[Pazuzu]

Originally Posted by La Quinta

I have a 1977 Carrera 3.0 with a proper 98mm conversion using Mahle Pistons and barrells. The engine was balanced to within 1gm during the rebuild and the ports and manifolds were matched. With SSI exhaust and new matched injectors the car delivers 205 bhp at the rear wheels. A big improvement on a claimed 200bhp at the flywheel.
Pressure fed tensioners and Dilivar studs were also included. The familiar Carrera 3 surge from 4000 rpm starts at about 3400rpm and it pulls so strongly at the top end the rev limiter is easily activated in 5th gear.
The car is on 7 and 8 x 16 with Bridgestones SO2 Uprated Bilsteins and thicker torsion bars and rear ARB

That has got to be an amazing engine!

[Hotwatermusic]

Originally Posted by Gunter

Good stuff but we need to know more.

Find out from the PO what the compression ratio is for the P/C's.
And, what cams were used? 964 ?
Is this a '78-'79 engine or a '80-'83?
With SSI heater boxes and what muffler?

Let us know more details.

It's an 83 engine, with, as far as I know, the stock ('83) heat exchangers and muffler. All of this is in a 74 body though. Wouldn't it have been smarter for the PO to have kept the '74 heat x'ers and exhaust? Also, the PO will have no idea what the compression ratio is...he didn't even know what size Fuch's was on the car. The only reason I believe the work was done is I have the receipt for it. But I don't see anything about cams on it. I think whatever is the easiest way to upgrade a 3.0 to a 3.2, that's how it was done. Cost about $3,400 when it was all said and done.

What I can say is the car is slower than molassess up to 3.5K, then unloads from there up to 5K. But I hear this rather normal.

[Paulporsche]

My car is a 3.2 similar to what you mention, in an S body. It is not slow up to 3500 @ all. The SSI exhaust, which is similar to the '74, is definitely better than the 83. I have been told my diz (which is from a 74-77) has been modded to advance faster than stock. Maybe that accounts for the quick pickup, along w/ my smaller dia tires. And that is w/ the 8:31 diff. I have about 10000 mi on that engine.

[racer]

My old '78 euro (3.0 with CIS) was modded much like mentioned above.. to a 3.2 (P/C change)with CIS. It dynod, over the years (differing dynos), with stock CIS cams, SSI's and a twin outlet sport muffler at 192 and 199 RWHP.. Similar TQ numbers. It was a nice smooth motor. It was "weaker" at higher RPM than a 3.2 Motronic motor, but certainly not shabby at all.. plus the Euro was a little lighter. I think it had better low end TQ than the 3.2 Motronic though.

[jvrrdrgz5]

I have a 1980 SC 3.0. Currently am running a Monty 2 in 1 out, SSI. Here is the plan:

Tbitz EFI
Perf Air box (open type)
3.2SS conversion to 9.81 CR
Super Cup Cams (fom the Camgrinder)
MSD ingnition and coil
Mag wires

The question i have is: what can I expect with this set up? I hear talk of sluggish movement in the low RPM and possible issues with reliability.

can any one shed light on this and maybe provide ideas for tunning.

[Gunter]

Make sure that the distributor has the right curve for the planned set-up.

I suggest you have it re-curved to run without vavuum; about $400.- to do.
The vac pod is removed, the inside plate is locked and the weights and springs are tweeked.

The '80 distributor has vac advance and retard and is not right for what you're planning but can be re-curved.

With 9.8 CR, single plug, you want to prevent detonation and that means using high octane, correct timing and watching air temps.

[tcar]

Check out the "Targa to Sicily" thread:

Targa to Sicily

juicesr has a 3.2SS, but a cam and homemade 2I/2O exhaust. Says it's very torquey in the thread.

[Rex Karrs]

I'm surprised nobody's mentioned the difference in the rod bolts. Original SC rod bolts are thicker than original 3.2 rod bolts, making them more amenable to high-RPM running.

[Michel J]

I went different route with my 3.0 to 3.2 conversion. I call it the the 3.2LS.
I swapped my 3.0 crank and rods for that of a 3.2, I used my (still good)3.0 cylinders with some JE pistons with a 9.3 CR, 964 cams etc.
I have yet to run it. It's waiting for the next project :-)

[Gunter]

Interesting.

Some people do that with 98 mm P/C's and make a 3.4 liter.

How did you work the different wrist pin sizes?
Like 22 mm in the SC pistons vs. 23 mm in the Carrera rods?
Bore out the pistons or modify the bushings?

And how did you check CR ?
Space between the pistons and heads?

[Michel J]

Rods are from a Carrera and JE pistons were designed for the same. CR was calculated using measured combustion chamber volume, and measured deck height taking account the stoke is now longer of course. I have the measurements somewhere.

I was going to build a 3.4 but decided to stay at 3.2 since it was highly recommended going to double plugs with a 98mm bore. Lots cheaper too!

[Michel J]

Main bearing was also machined for better oiling of number 4 rod bearing (I think that is the one) that is know to fail.